For this study, Lutcavage, Galuardi and fishermen partners deployed 58 miniature pop-up satellite archival tags (PSAT) and 132 implanted archival tags on juvenile Atlantic bluefin tuna between 2005 and 2009. Because only one archival tag was retrieved, data reported are mainly from 26 PSATs.
To deploy the PSATs, fish were caught by hook and line and brought aboard the boat to attach a miniaturized PSAT to the fish's fin by a tether and dart anchored at the base of the fin. These were programmed to record external temperature, depth and daily position based on light sensor readings every 15 minutes and to release after 12 months. Later models also recorded light level. Once at the surface, the PSAT tags transmitted the collected data to receivers on earth-orbiting satellites. The data were then transmitted to the researchers, allowing scientists to trace the fish's journeys and habitat over the previous year.
The authors report that all tagged bluefin tuna remained in the northwest Atlantic for the duration observed, and, in summer months they stayed in coastal waters from Maryland to Cape Cod out to the continental shelf. In the winter, they wandered more widely, exiting the Gulf of Maine and ranging south to the South Atlantic Bight (North Carolina to Florida), the northern Bahamas and the Gulf Stream edge.
Lutcavage and Galuardi found that vertical habitat patterns showed juvenile bluefin primarily occupied shallow depths, averaging about 16 to 40 feet (5 to 12 meters) and relatively warm water, averaging 64 to 70 degrees F (about 18 to 21 degrees C). In winter, they frequented deeper water and showed more variable depth patterns.
"These findings are the first long-term view into a year in the life of a juvenile bluefin tuna in the western Atlantic," Lutcavage notes. "The geographic and vertical concentration of summer habitat had been suspected due to
|Contact: Janet Lathrop|
University of Massachusetts at Amherst